US 4,225,576 AGranted

Combined radioimmunoassay for triiodothyronine and thyroxine

AssigneeMiles Laboratories, Inc.

InventorsCharles E. Denning, Lloyd A. Schick

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Abstract

A method for the combined radioimmunoassay for the hormones triiodothyronine (T-3) and thyroxine (T-4) in serum or plasma, wherein the radiolabeled T-3 and T-4 reagents are T-3 and T-4 labeled with the same radioisotope. The hormones are extracted from the serum or plasma sample and separated from their binding proteins by adsorption to a crosslinked dextran gel at a highly alkaline pH. After washing away the dissociated proteins, a predetermined limiting amount of T-3 antibody is incubated with the gel and thereafter radiolabeled T-3 which has become extracted from the gel by antibody binding is washed away. Excess T-3 antibody and a predetermined limiting amount of T-4 antibody are then incubated with the gel and radiolabeled T-3 and T-4 which has become extracted from the gel by antibody binding are thereafter washed away. The respective relative amounts of radiolabeled T-3 and T-4 retained by the gel after the incubations with the respective limiting amounts of T-3 and T-4 antibody are compared with standard results to quantitate the hormones in the sample. The use of excess T-3 antibody in the T-4 antibody incubation is critical to the accuracy of the method, enabling the use of the same radioisotope for radiolabeling T-3 and T-4.

Claims9

Dependent claims

A method for the combined radioimmunoassay for triiodothyronine (T-3) and thyroxine (T-4) in a serum or plasma sample comprising the steps of:

(a) contacting a crosslinked dextran gel at a pH of at least 11 with said sample and with radiolabeled T-3 and T-4 labeled with the same radioisotope,
(b) washing said gel with an alkaline aqueous solution having a pH less than 11,
(c) incubating said gel with a predetermined first amount of an antibody to T-3 insufficient to bind all of the radiolabeled T-3 bound to said gel at the conclusion of step(b),
(d) washing said gel with an alkaline solution having a pH less than 11, said gel retaining a portion of the radiolabeled T-3 bound thereto as a direct function of the amount of T-3 present in said sample,
(e) incubating said gel with a predetermined second amount of an antibody to T-3 sufficient to bind all of the radiolabeled T-3 bound to said gel at the conclusion of step(d) and with a predetermined amount of an antibody to T-4 insufficient to bind all of the radiolabeled T-4 bound to said gel at the conclusion of step(d),
(f) washing said gel with an alkaline aqueous solution having a pH less than 11, said gel retaining substantially no radiolabeled T-3 while retaining a portion of the radiolabeled T-4 bound thereto as a direct function of the amount of T-4 present in said sample, and
(g) comparing (1) the relative amounts of radiolabeled T-3 and T-4 retained by said gel after washing steps(d) and (f), respectively, with respect to the amounts of radiolabeled T-3 and T-4 contacted with said gel in step(a), to (2) such relative amounts obtained by performing the same method on standard samples containing known amounts of T-3 and T-4.

4 more elements

Dependencies are inferred from the claim text.

Facts

Application: 05/962,398Filed 20 Nov 1978
Granted: 30 Sep 1980
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

G01N 33/78
Involving hormones or other non-cytokine intercellular protein regulatory factors such as growth factors, including receptors to hormones and…:…
Y10S 436/804
Chemistry: analytical and immunological testing: radioisotope, e.g. radioimmunoassay
Y10S 436/825
Chemistry: analytical and immunological testing: pretreatment for removal of interfering factors from sample
G01N
Investigating or analysing materials by determining their chemical or physical properties